Forward and backward electron emission in binary cell of radioisotope current source
It was shown that ratio of forward and backward yields for Ti-Ti binary cell of the SERICS was close to other materials. Isotropic emission of alpha particles from the surface of radioisotope source led to dependency of projectile effective charge and convoy electron yield on incidence angle. The in...
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irk-123456789-1122042017-01-19T03:02:15Z Forward and backward electron emission in binary cell of radioisotope current source Kononenko, S.I. Zhurenko, V.P. Kalantaryan, O.V. Semerenskiy, A.A. Приложения и технологии It was shown that ratio of forward and backward yields for Ti-Ti binary cell of the SERICS was close to other materials. Isotropic emission of alpha particles from the surface of radioisotope source led to dependency of projectile effective charge and convoy electron yield on incidence angle. The influence of convoy electrons on total electron yield can be neglected. Показано, що відношення електронних виходів у прямому і зворотному напрямках для Ti-Ti-бінарної комірки SERICS близьке до деяких інших матеріалів. Ізотропне випромінювання альфа-частинок з поверхні радіоізотопного джерела призвело до залежності ефективних зарядів і виходу конвойних електронів від кута взаємодії. Впливом конвойних електронів на загальний вихід електронів можна знехтувати. Показано, что отношение электронных выходов в прямом и обратном направлениях для Ti-Ti-бинарной ячейки SERICS близко к некоторым другим материалам. Изотропное испускание альфа-частиц с поверхности радиоизотопного источника привело к зависимостям эффективных зарядов и выхода конвойных электронов от угла взаимодействия. Влиянием конвойных электронов на общий выход электронов можно пренебречь. 2015 Article Forward and backward electron emission in binary cell of radioisotope current source / S.I. Kononenko, V.P. Zhurenko, O.V. Kalantaryan, A.A. Semerenskiy // Вопросы атомной науки и техники. — 2015. — № 4. — С. 331-334. — Бібліогр.: 17 назв. — англ. 1562-6016 PACS: 79.20 http://dspace.nbuv.gov.ua/handle/123456789/112204 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Приложения и технологии Приложения и технологии |
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Приложения и технологии Приложения и технологии Kononenko, S.I. Zhurenko, V.P. Kalantaryan, O.V. Semerenskiy, A.A. Forward and backward electron emission in binary cell of radioisotope current source Вопросы атомной науки и техники |
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It was shown that ratio of forward and backward yields for Ti-Ti binary cell of the SERICS was close to other materials. Isotropic emission of alpha particles from the surface of radioisotope source led to dependency of projectile effective charge and convoy electron yield on incidence angle. The influence of convoy electrons on total electron yield can be neglected. |
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Article |
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Kononenko, S.I. Zhurenko, V.P. Kalantaryan, O.V. Semerenskiy, A.A. |
| author_facet |
Kononenko, S.I. Zhurenko, V.P. Kalantaryan, O.V. Semerenskiy, A.A. |
| author_sort |
Kononenko, S.I. |
| title |
Forward and backward electron emission in binary cell of radioisotope current source |
| title_short |
Forward and backward electron emission in binary cell of radioisotope current source |
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Forward and backward electron emission in binary cell of radioisotope current source |
| title_fullStr |
Forward and backward electron emission in binary cell of radioisotope current source |
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Forward and backward electron emission in binary cell of radioisotope current source |
| title_sort |
forward and backward electron emission in binary cell of radioisotope current source |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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2015 |
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Приложения и технологии |
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http://dspace.nbuv.gov.ua/handle/123456789/112204 |
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Forward and backward electron emission in binary cell of radioisotope current source / S.I. Kononenko, V.P. Zhurenko, O.V. Kalantaryan, A.A. Semerenskiy // Вопросы атомной науки и техники. — 2015. — № 4. — С. 331-334. — Бібліогр.: 17 назв. — англ. |
| series |
Вопросы атомной науки и техники |
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2025-07-08T03:32:13Z |
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| fulltext |
ISSN 1562-6016. ВАНТ. 2015. №4(98) 331
FORWARD AND BACKWARD ELECTRON EMISSION IN BINARY
CELL OF RADIOISOTOPE CURRENT SOURCE
S.I. Kononenko, V.P. Zhurenko, O.V. Kalantaryan, A.A. Semerenskiy
V.N. Karazin Kharkiv National University, Kharkov, Ukraine
E-mail: sergiy.i.kononenko@gmail.com
It was shown that ratio of forward and backward yields for Ti-Ti binary cell of the SERICS was close to other
materials. Isotropic emission of alpha particles from the surface of radioisotope source led to dependency of projec-
tile effective charge and convoy electron yield on incidence angle. The influence of convoy electrons on total elec-
tron yield can be neglected.
PACS: 79.20
1. INTRODUCTION
1.1. BACKGROUND
An ion propagating through a matter produces free
electrons, some of which, with the proper values and
directions of momentum, can escape from the medium.
This process is called ion induced electron emission
(IIEE). At present, it is proved theoretically and experi-
mentally that the IIEE coefficient in the case of light
ions is directly proportional to the mean specific ioniza-
tion loss dE/dx of an ion in a matter [1, 2]. Consequent-
ly, the investigation of SEE makes it possible to derive
information about the energy lost by an ion as it moved
through a solid-state plasma and about how this energy
is distributed between different electron groups. The
mean specific ionization loss dE/dx of an ion at each
point in a medium can be represented as a sum of the
losses associated with energy transfer to the electrons
that move in the same direction as the primary ion,
(dE/dx)F, and with the energy transfer to the electrons
that move in the opposite direction, (dE/dx)B:
dE/dx = (dE/dx)F+(dE/dx)B. In our opinion, it is quite
natural that the quantities (dE/dx)F and(dE/dx)B are pro-
portional to the coefficients of IIEE in the propagation
direction of a fast light ion (in the forward direction),γF ,
and in the opposite (backward) direction, γB , respective-
ly. Hence, by investigating the kinetic ion-electron
emission from a thin film in the forward and backward
directions, it is possible to study the anisotropy of ener-
gy transfer from a primary ionizing charged particle.
In the energy spectrum of the secondary emission
electrons we can distinguish three electron groups:
1. Slow electrons with energies E < Ep, where Ep = hωp
is the energy of the plasma oscillations with fre-
quency ωp. These electrons are produced from the
ionization by plasma oscillations and from direct
collisions with large impact parameters, accompa-
nied by small momentum transfers.
2. Moderate-energy electrons, which are produced ex-
clusively in direct collisions accompanied by mod-
erate momentum transfers.
3. Fast electrons, which move preferentially in the
propagation direction of the ion. These are convoy
electrons and δ-electrons, which produced from di-
rect collisions with small impact parameters, accom-
panied by large momentum transfers. The velocity
convoy electrons, coincides in magnitude with the
velocity of the ion, ve = vp, and has the same direc-
tion. The velocity of the δ-electrons that corresponds
to the maximum possible momentum transfer can be
defined as vδ = vpcosθ, where vp is the velocity of a
bombarding ion and the angle θ is measured from its
propagation direction.
1.2. SECONDARY EMISSION RADIOISOTOPE
CURRENT SOURCE
New technique for nuclear decay energy conversion
to electrical was based on the power law distribution of
emission electrons induced by ions. This phenomenon
was predicted theoretically early [3]. Some differences
between the experimental values and theoretical power
law indexes were related with the time evolution of the
electron distribution function [4]. Main channel of fast
ion energy loss in matter is processes of atom ionization
[5]. At that part of substance electrons can leave the
surface leading to a secondary ion-induced electron
emission [6 - 8]. The integral characteristic of the emis-
sion is coefficient γ frequently called in the literature as
an electronic yield [6 - 8]. Emission coefficient is de-
fined as a relation of a number of secondary electrons
Ne emitted to a number of primary incident ions Ni:
γ=Ne/Ni. (1)
Coefficient γ can vary depending on ion energy, tar-
get substance and a number of other parameters [6 - 8].
Fig. 1. Schematic diagram of SERICS: 1 – vacuum
container; 2 − α-radioisotope; 3 and 4 – emitting thin
layers with different emission coefficients
By using α-particles emitted by radioisotope as pro-
jectiles and pair of thin emitting layers (insulated from
each other) with different coefficients γ it is possible to
convert energy of nuclear particles into electricity. This
idea underlies secondary emission radioisotope current
source (SERICS) [9 - 11].
SERICS schematic diagram is presented on Fig. 1.
Radioisotope 2 emitting α-particles towards two half-
ISSN 1562-6016. ВАНТ. 2015. №4(98) 332
spheres is situated in vacuum container 1. Two emitters
of electrons are located on both sides of the radioiso-
tope. Each emitter is a set of some pairs of thin emitting
layers (so-called binary cells) of two different materials
3 and 4. One of the materials should have high emission
coefficient, whereas the other should have low one. All
of the layers are parallel and insulated with each other.
Layers from one material electrically connected in par-
allel and have own contact. As α-particle passes through
emitter, difference of charges between the layers of bi-
nary cell arises. By close the circuit with useful load it is
possible to use the charge difference as a source of cur-
rent. Effectiveness of energy conversion is proportional
to the number of emitting pairs N and difference of the
emission coefficients [6].
Fig. 2. Binary cell of SERIC: 1 − layer of higher IIEE
yield (γ1); 2 − layer of lower IIEE yield (γ2);
σ1 and σ2 SEEE yields respectively
The basis of SERICS is a binary cell which consists
of two different materials (Fig. 2). We established that
secondary electron-electron emission (SEEE) (tertiary
emission) influenced strong at efficiency of SERICS.
Titanium and some other materials have SEEE yield
less than one. We carried out forward and backward
emission study for Ti-Ti binary cell. The results are pre-
sented in this paper.
2. THE EXPERIMENTAL SETUP
The experiments were carried out with the device,
which schematic diagram is shown in Fig. 3.
Fig. 3. The experimental device: 1 – vacuum chamber;
2 – Pu239 radioisotope source of α-particles;
3 – target; 4 – movable diaphragm; 5 – collector;
6 – B5-50 dc source; 7 – electrometric voltmeter
The prototype of the binary cell, consisting of radio-
isotope source of α-particles with Pu-239 isotope 2, the
emitter of a titanium foil 3 and the Ti massive collector
5, were placed in a vacuum cylinder chamber 1. The
radioisotope source 2 produced α-particle flow with
intensity of 4.64⋅106 particles/s and energy of
5.15 MeV. The alpha-particles current Ic0 was measured
of multiple Faraday cylinder collector. The titanium foil
thickness of 5.6 µm was chosen to be less than a mean
path of α-particle with given energy in this material.
The α-particle passed through the emitter 3 and induced
the electron emission from the forward emitter surface
and from the surface of the massive collector 5. The
measurements of a collector current were made by an
electrometric voltmeter 7 with input impedance of
1016 Ohm. Voltage of different polarities was applied to
the emitter-collector gap and was changed from 1 to
300 V. For adjusting the system a moveable damper 4,
shutting the flows of α-particles and emitted electrons,
was placed between the emitter and the collector. The
residual gas pressure in the vacuum chamber was less
than 10-4 Pa. The chamber was pumped out with a mag-
netic discharge pump 9 and mechanical rough pump
with a nitrogen-cooled trap.
3. THE EXPERIMENTAL RESULTS
AND DISCUSSION
The collector current as a function of voltage applied
between the titanium foil (as emitter) and titanium plate
(as collector) is shown in Fig. 4.
Fig. 4. The experimental current-voltage character-
istics for Ti-target and Ti-collector
This coefficient γ for forward and backward cases
was calculated by the following formulas:
0
0
2 ,f c
F
f
k I I
k I
α
α
γ
+
= 0
0
2 f c
B
f
k I I
k I
α
α
γ
−
= , (2)
where Ic is the collector current and kf is the fraction of
alpha-particles that have passed through the target. The
ratio R of the forward IIEE coefficient γF to the back-
ward one γB, was measured earlier and was equal to 1.57
for aluminum, 1.69 for copper, and 1.82 for nickel [13].
We found thatR ratio for titanium was equal to 1.62.
According to these data, the R ratio for different sub-
stances varies insignificantly (lower than 10% of the
mean value).
The charge of moving projectile in matter depends
on its velocity. In our case, different incidence angles
for alpha particles led to various effective charges on
the target surface. Analytical formula for effective
charge Z eff calculation according to the Bohr model was
obtained in [12]:
ISSN 1562-6016. ВАНТ. 2015. №4(98) 333
−−= 3/2
20
1
1 exp1
Zv
vZZeff , (3)
where Z1 and Z2 are charges of projectile and target at-
oms respectively, v1 is projectile velocity, v0 is Bohr
velocity. The best agreement with experiment is given
by the formula obtained in [13]
−−= 3/2
20
1
1 92,0exp1
Zv
vZZeff . (4)
When fast ions penetrate a solid or gaseous medium,
they can be accompanied by electrons which move at
nearly the same velocity as the ion. These electrons
have been called convoy ones [15]. Influence of differ-
ent interaction parameters on convoy electrons was
studied in many investigations (see for example [16,
17]). Authors [17] summarized their experimental re-
sults by the empirical equation for yield of convoy elec-
trons:
4 2,75 2,25
11 10 ( )c T effC Z Z Eγ − −= × , (5)
where Zeff is the effective charge of the incident particle
with energy E1 in MeV/amu, and C is a constant de-
pending on the target material; C(Au) = 1.65, C(Ag) =
1.25, C(A1) = C(C) = 1.0. All the values have accuracy
0.15.
Alpha particles were emitted isotropically from the
surface of radioisotope source. These projectiles moved
at different angles with respect to the target surface and,
consequently, passed different path in the matter of the
foil. As a result, their energy losses were different too
(Fig. 5).
0 10 20 30 40 50 60 70 80
0
1000
2000
3000
4000
5000
E,
K
eV
θ, deg
Fig. 5. Dependence of alpha-particle energy at the back
surface of the titanium foil
0 10 20 30 40 50 60 70 80
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
Ze
ff,
a
rb
.u
n.
θ, deg
Fig. 6. Effective charge of alpha-particles in the target
foil as function of incidence angle
The effective charge is a function of projectile ve-
locity. Consequently, it depends on the incidence angles
too (Fig. 6).
In this case, yield of convoy electrons according (5)
varied from 5.7·10-4 (0°) to 0.82 (75°). The influence of
convoy electrons on total electron yield can be neglect-
ed. However, these electrons have considerable energy
from 578 eV (0°) to 71 eV (75°). It means that convoy
electrons enable to knock out secondary electrons from
the opposite electrode. These additional electrons influ-
ence on charge balance between the electrodes and de-
crease the conversion efficiency of SERICS.
CONCLUSIONS
In this paper the investigation of the forward and
backward electron emission in Ti-Ti binary cell of the
SERICS induced by alpha-particles have been carried
out. It was shown that ratio of forward and a backward
yield was close to the other materials. Isotropic emis-
sion of alpha particles from the surface of radioisotope
source led to distribution of the projectile’s energy in
binary cell. As a result, the effective charges of projec-
tile and convoy electron yield depend on incidence an-
gle of alpha-particles. The influence of convoy electrons
on total electron yield can be neglected.
ACKNOWLEDGEMENTS
We would like to appreciate the great contribution of
Prof. V.I. Karas’ to the formulation of the problem and
productive discussion of the experimental results.
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10. V.M. Balebanov et al. Secondary emission radioiso-
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Article received 28.05.2015
ЭЛЕКТРОННАЯ ЭМИССИЯ ВПЕРЕД И НАЗАД В БИНАРНОЙ ЯЧЕЙКЕ РАДИОИЗОТОПНОГО
ИСТОЧНИКА ТОКА
С.И. Кононенко, В.П. Журенко, О.В. Калантарьян, А.А. Семеренский
Показано, что отношение электронных выходов в прямом и обратном направлениях для Ti-Ti-бинарной
ячейки SERICS близко к некоторым другим материалам. Изотропное испускание альфа-частиц с поверхно-
сти радиоизотопного источника привело к зависимостям эффективных зарядов и выхода конвойных элек-
тронов от угла взаимодействия. Влиянием конвойных электронов на общий выход электронов можно прене-
бречь.
ЕЛЕКТРОННА ЕМІСІЯ ВПЕРЕД І НАЗАД У БІНАРНІЙ КОМІРЦІ РАДІОІЗОТОПНОГО ДЖЕРЕЛА
СТРУМУ
С.І. Кононенко, В.П. Журенко, О.В. Калантар’ян, А.А. Семеренський
Показано, що відношення електронних виходів у прямому і зворотному напрямках для Ti-Ti-бінарної
комірки SERICS близьке до деяких інших матеріалів. Ізотропне випромінювання альфа-частинок з поверхні
радіоізотопного джерела призвело до залежності ефективних зарядів і виходу конвойних електронів від кута
взаємодії. Впливом конвойних електронів на загальний вихід електронів можна знехтувати.
1. INTRODUCTION
1.2. secondary emission radioisotope current source
3. The experimental results and discussion
references
|